Invasive plant in Norwood Lake that chokes out native species ‘here to stay,’ say researchers

Saturday, December 8, 2012 - 8:31 am

NORWOOD – While the invasive plant Eurasian watermilfoil “is here to stay” in Norwood Lake, Clarkson researchers say there are several options for managing the plant.

This past summer the invasive aquatic plant was detected in Norwood Lake, a fluvial lake created by a dam on the Raquette River at Norwood. The plant is one of the nation's most widespread invasive aquatic plants and has already invaded more than 50 lakes in New York's Adirondack State Park.

Proliferation of the plant in lakes tends to choke out native aquatic plant species and reduce optimal game fish habitat. It also can interfere with boating and swimming.

“This plant is very capable of spreading rapidly due to its range of tolerances, its rapid growth rate, and ability to easily spread by growth of plant fragments,” says Clarkson University Biology Professor Michael Twiss.

Twiss and his students of limnology – the study of freshwater bodies – decided to examine the invasion in Norwood Lake with the aim of recommending sustainable management practices to control the plant.

“This plant is here to stay,” says Twiss. “However, various options are available to manage this invasive species.

“Our students have looked carefully into various techniques used elsewhere and have discounted some based on high cost or those ill-suited for use in this system, such as use of herbicides. For example, mechanical harvesting is too costly and can cause increased spread by fragments downstream. Hand harvesting is equally expensive. Moreover, it has cost hundreds of thousands of dollars to control this plant in Upper Saranac Lake, and it remains there.”

Sustainable options will likely require coordination among the local government, residents, and Brookfield Power, the company controlling the dam at Norwood Lake, the students told an audience at the Norwood Municipal Building Thursday.

Winter drawdown of water levels has been used to kill Eurasian watermilfoil in other water-level regulated lakes, but it also kills native plants and would require a deviation from agreed water level regulation.

Allowing the plants to spread naturally will eventually lead to self-control as natural pests would increase and serve to reduce the population. But it could take as long as 10 years to come to equilibrium, and might not result in a suitable outcome due to the detrimental impact the plant likely would have on the recreational value of the lake, a focal point in the community.

Lake stewards that can assist in educating the public and help prevent spread of the plant could be involved with environmental monitoring in the lake to determine the rate of spread, and gather other information needed to determine the best solution for all stakeholders.

“Control efforts have to be sustained from year to year to set up management projects for success,” says Twiss. “Discussion needs to take place now so that the community can be prepared for making decisions on the choice of a sustainable management plan to maintain the value of this important regional water resource."